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yMOSES G. FARMER, OF SA'LEM, MASSACHUSETTS.

Letters Patent No. 113,864, dated April 18.1871.

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To all whom it may concern: Be it known that I, Mos'ss G. Funnix-neef Salem, in the county of Essex and State of Massachusetts, have invented au Improved.Thermo-Electric Pair; and I do hereby declare that the^following, taken iu connectionwith the drawing which accompanies and forms part of this specification, isa description of my invention'suiicient to enable those skilled in the art to practice it. g

It has been known for many years that, by joining the endsof two bars 'of dierent metals and heating them at one of their junctions au electric current can be excited, provided Vthe other ends of the bars are kept ata lower temperature. Such currents' have been so feeble, however, that batteries formed of such elements havebeen but little used, vexcept in the hands of scientific men,vfor determining temperatures.

They have been known as meilonis, and have gener ally been constructed of antimony and bismuth, a stronger current being obtained with thesemetals than with any others.

It hasalso been known that a stronger current can be obtained from certain alloys than from any of the .pure metals.`

Bue of the most eeotive combinations is that of a German-silver bar in conjunction with a bur formed from an alloy of antimony and zinc. -These Vtwo alloys are cheap enough for common use, and have a melting poiut-sutiicentl-y high to admit of a large diher- :game in temperature between the opposite ends o f the Qn the other hand the alloy of antimony and zinc,

v iu the proper proportions 4to produce au ecieut current, is exceedingly brittle, and itis difficult to join a bar of it to a bar of German vsilver or other metal so as to secure a. union of the two which will not be so imperfect as to offer great resistance to the current;

Moreover, ythe' alloy of antiuiony and zinc has so great a specific resistance to the electriccurrent that it is desirable to give to the bars formed from it a large v cross-section`in `proportion to the cross-section of the 'German-silver element of the pail".

'f For the same reason it is importantto bring a largesurface into contact with the German silver at the junction. l

It is also desirable'that 'thewhole of the surface in contact should -be uniformly heated. especially when large, iu order that cross-currents may `not be .pro-

duced by a difference in the tempcratilres` of'diiferentmay be easily combined into one battery without interfering with the conditions necessary forapplying the heat easily and uniformly to the junctions of the several pairs combined.

The object of my present'l invention is to secure these conditions and advantages, to accomplish which I construct the bars as follows:

The German-silver bar is bent so that the part which is to be joined tothe 'antimony-znc bar shall extend over the end of the latter, while thc other part lies parallel to its side.

This mode of construction will be readily understood from the drawing, where the antimony-ziuc bar is represented by a and the Gcrmansilrcr bar is 4represented by b c`, the part c beiugthepart which is joined to the antimouy-zinc har.

The part bof the Gcrmawsilver bar is to be insulated from the antmony-z'inc bar by some non-conducting substauce, like mica, shown at in.'

Itis importantthntthe two 'bars shall be joined together'as perfectly as possible.

The -best method I have found to do this is to place the German-silver har, when properly prepared, in a mold of the, proper shape, and to cast the antimonyzinc bar upony it. The German silver is bent to the proper shape, and that-part of it which is to he joined to the autmony-zinc bar is provided with projections 4or pins, which are to enter the end of thc' antiuionyzinc bar. Theohject of these projections is to aid tho adhesionof the two barsto cach other. They-may he formed in a variety of ways, such as by drilling holes intoithe German silver and inserting pins so that these pins shall project into the alloy of autilnony and ziucwhen it is cast upon them.

Still another way is to punch partly .out Iiomthe German silver V-shaped .portions of it, and turn them up so as to project into the alloy.- By such means the German-silver bar can be caused to take fast holdv upon 'the antimon'y-zinc bar.

' These spurs or projections are represented by d d V in the drawing.

In order that the union between theGerman-silvcr bar and theantimony-zinc .bar may be of the most in.-

, timate character, it is important to first cleanse the surface 'oftheerman sil ve'r and its projections thor oughly. This is best done by h ninersing it fora time in a dilhte solution of'sulphuric ncid': then the end of the German silver-is coated vby dipping itfirst int-o a solution of. the donblewhloride of zinc and ammonia,

(common solderingacid,)` andaiterward into a melted y alloy ofl about two partsltiu and one of `zinc. This l gives a bright surface, to whichmelted antimony-zinc readily adhereswhen it, is poured upon it.

A strip of German silver', or ofy copper'tiuned with ordinary tinning'solder, is also insertd'into the mold so as to be joinedl to the opposite end of the antimonyzinc bar, (by theoperation of casting,) as seen in the drawing, where such stripis represented by e, said, strip forming the continuotlon'of the circuit when the pair is in operation. Q When the mold is thus l,prepared by the introduction of the' Gennan-silver bar'and melted n'ntixnony-zinc is poured intol lthe mold, and when cold the two bars and the piece e will be tlnnly joined together. The mica for separating-the German silver from the antimony-zinc in the mold by the side ofthe German'silver, and the melted antimony-zinc be then poured into' the incid;

or it may be inserted between the two after the pair is formed. I prefer the lstr mode.

y I have found in my'experience far thaLt-it-isv y bar may be placed use better, on account of two alloys, that the linear dimensions ofthe antimonypair with the two elements lying side by side, but joined together across the end o f one ot them, substantially as described.

2. Projections upon one of' the' bars to aidfin joining the t'wo bars, substantially as described.

MOSES G. FARM-EB.

Witnesses:

,J. B. CROSBY,

FRANCIS GoUnn.

the unequal expansion of theA 

